Analysis of "Stubbing Effect" and Its Utilization in Wind Farms

The “stubbing effect” is an important part of the influence of terrain on wind speed, and relevant international organizations have included it in the 20 new urban disasters facing the metropolis. Due to the small distance between the high-rise buildings in the city, the wind can not pass smoothly after the face blows. It can only be gathered in a small space. When strong winds come, the high-rise buildings will lead high-altitude strong winds to the ground, causing local strong winds near the high-rise buildings. The tube effect is not only easy to cause a flying accident, but also affects the safety of pedestrians. It may even appear that pedestrians in the wind near high buildings are difficult to walk and are blown down by the wind.

Let us first look at the definition of the narrow tube effect:

When the airflow flows from the open area to the canyon formed by the terrain, the air quality cannot be accumulated in a large amount, so that the wind flows faster and the wind speed increases. When flowing out of the canyon, the air flow rate will slow down again. The effect of this canyon topography on airflow is called the “stubbing effect” or the “canyon effect”.

A simple schematic diagram is represented, as shown in the windward side stream is pressed, the wind speed in the accelerating channel, to form a "funneling air." (In the wind farm, we generate funneling effect which increases the influence of topography The wind is called the canyon wind or the wind.)

The adverse effects of the narrow tube effect were not only in the city. On February 28, 2007, 5,807 passenger trains from Urumqi to Aksu were attacked by a 13-level gust, causing the vehicle to derail. The location of the accident is the canyon area from the north to the south of the Tianshan Mountains. When the wind passes through this terrain and is the tuyere, the wind will multiply after the rapid expansion of the “sinusoidal effect”, and its destructive power is amazing.

For example, in the Hexi Corridor area, due to the narrow tube effect caused by the terrain, the wind speed near the surface is obviously enhanced, and strong sandstorms or extremely strong sandstorms often occur in the Hexi area. From March to May each year, the active cyclone and cold air activities in Mongolia are prone to windy weather; the desert area is less rainy, the weather is warmer, and the temperature is rising, which is very easy to promote the formation of sandstorms.

So, after reading the above examples, can we simply classify the “stubbing effect” as a climate disaster?

In fact, there are two things in everything, and the narrow tube effect will have many adverse effects, but there are certain opportunities for the development and construction of wind farms.

For example, the narrow channel effect formed by the Taiwan Strait between Fujian Province and Taiwan Province and the perennial northeast wind has increased the wind speed on the coasts and islands of Fujian, and the wind speed can be extended.

Let's talk about the Hexi Corridor. This area is known as the “wind power corridor” in China because the Hexi area is close to the winter wind source; the terrain is flat, the vegetation coverage is low, and the wind is large. The influence of the terrain leads to a narrow tube effect, and the surface wind speed is strong. As shown below.

For example, in the cold lake T-junction area of ​​Qinghai, due to the influence of terrain, there is a relatively obvious narrow tube effect. As shown in the following figure, there are high peaks on the north and south sides of the 305 provincial road at T-junction. At the same time, the wind direction and the prevailing wind energy direction in the cold lake area are all E, and the terrain is flat and the surface obstacles are scarce. The rate is low and affected by the narrow pipe effect. The wind speed in this area is relatively strong, which is conducive to the construction of wind power .

From the perspective of fluid mechanics, the wind is squeezed in the canyon, the wind speed becomes larger, and the flow becomes chaotic, changing from the laminar flow state of the open space to the turbulent state, so that the destructive speed can be achieved, and the wind turbine can be easily The adverse effects have formed certain challenges for the development and construction of wind farms and the utilization of wind energy.

From this we can simply summarize that the narrow tube effect of wind energy acceleration can be utilized in wind power generation, which requires certain conditions, mainly including two points: First, the prevailing wind direction of the area is consistent with the direction of the narrow tube, and the prevailing wind direction is concentrated. . Second, the terrain is relatively simple, the surface of the airflow channel forming the narrow tube effect should be as smooth as possible, otherwise large turbulence will occur, which will adversely affect the wind turbine .

Canyon wind farms have their own special characteristics, and they have their own characteristics for different terrain effects. Survey and design work is also difficult. However, as long as the characteristics of the wind energy resources of the canyon wind farm are mastered and its characteristics are analyzed and rationally utilized, the narrow pipe effect can also become a booster for the development and construction of wind farms.

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